In a powertrain having an internal combustion engine coupled to a transmission, a 12-volt DC auxiliary starter motor can be selectively energized to rotate a crankshaft of the engine and thereby start the engine. Hybrid powertrains use an engine in conjunction with one or more electric machines to optimize powertrain efficiency. One type of hybrid electric powertrain uses a belted-alternator-starter (BAS) in which the electric machine is coupled to the crankshaft, e.g., via a belt and pulley system. The auxiliary starter motor or the electric machine may be used to start the engine in some powertrain configurations, with torque from the engine used to power the electric machine in a generator mode to recharge an electrical storage system.